[rcore] No suitable DRM connector found on Raspberry Pi with composite output

[emdzej]

Issue description

When using composite output only on Raspberry Pi Zero W, when trying to initialise raylib the output is as follows:

INFO: DISPLAY: No graphic card set, trying platform-gpu-card
INFO: DISPLAY: Failed to open platform-gpu-card, trying card1
INFO: DISPLAY: Failed to open graphic card1, trying card0
TRACE: DISPLAY: Connectors found: 1
TRACE: DISPLAY: Connector index 0
TRACE: DISPLAY: Connector modes detected: 4
TRACE: DISPLAY: DRM mode NOT connected (deleting)
WARNING: DISPLAY: No suitable DRM connector found
WARNING: TEXTURE: Failed to load texture
WARNING: TEXTURE: Failed to load default texture

Environment

Raylib 5.0 compiled from source on Raspberry Pi Zero w Linux 6.6.31+rpt-rpi-v6 #1 Raspbian 1:6.6.31-1+rpt1 (2024-05-29) armv6l GNU/Linux

Code Example

Used core_basic_window.c from examples.

Investigation

The issue seems to be related to the code in rcore_drm.c

if ((con->connection == DRM_MODE_CONNECTED) && (con->encoder_id))
        {
            TRACELOG(LOG_TRACE, "DISPLAY: DRM mode connected");
            platform.connector = con;
            break;
        }
        else
        {
            TRACELOG(LOG_TRACE, "DISPLAY: DRM mode NOT connected (deleting)");
            drmModeFreeConnector(con);
        }

because in my case the connector status is unknown as can bee seen on modetest -c output:

trying to open device 'vc4'...done
Connectors:
id	encoder	status		name		size (mm)	modes	encoders
45	44	unknown	Composite-1    	0x0		4	44
  modes:
	index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot
  #0 720x480i 29.97 720 736 800 858 480 486 492 525 13500 flags: nhsync, nvsync, interlace; type: preferred, driver
  #1 720x576i 25.00 720 732 796 864 576 581 587 625 13500 flags: nhsync, nvsync, interlace; type: driver
  #2 720x288 50.08 720 740 804 864 288 290 293 312 13500 flags: ; type: driver
  #3 720x240 60.05 720 734 798 858 240 243 246 262 13500 flags: ; type: driver
  props:

Dirty solution

While this seems like the OS / hardware? issue which reports unknown status of the connector (or maybe it's not supported at all in certain hardware configurations), I was wondering if this could be a valid case to inlcude as an option in the library, to overcome this limitation.

Doing a cheap and dirty fix like this

        if (
            ((con->connection == DRM_MODE_CONNECTED) || (con->connection == DRM_MODE_UNKNOWNCONNECTION))
            && (con->encoder_id)
           )
        {
            TRACELOG(LOG_TRACE, "DISPLAY: DRM mode connected");
            platform.connector = con;
            break;
        }
        else
        {
            TRACELOG(LOG_TRACE, "DISPLAY: DRM mode NOT connected (deleting)");
            drmModeFreeConnector(con);
        }

solves the problem. Not sure what would be other implications of such a change, but anyway reporting it for anyone interested.

[raysan5]

@emdzej The "cheap and dirty" fix looks good enough to me, feel free to send a PR!

[emdzej]

Will do shortly. Thanks.